U.S. patent number 5,447,602 [Application Number 08/112,779] was granted by the patent office on 1995-09-05 for process for repulping wet-strength paper.
This patent grant is currently assigned to Henkel Corporation. Invention is credited to Stephen A. Fischer, James R. Heyward, Jr., Jerome S. Sajbel, Share.
United States Patent |
5,447,602 |
Sajbel , et al. |
September 5, 1995 |
**Please see images for:
( Certificate of Correction ) ** |
Process for repulping wet-strength paper
Abstract
A process for repulping wet-strength paper containing at least
one wet-strength resin in which a hydroperoxide alone or in
combination with a non-alkali, non-alkaline earth metal salt or
chelate is used to separate the resin from the wet-strength
paper.
Inventors: |
Sajbel; Jerome S. (Ft. Mill,
SC), Heyward, Jr.; James R. (Charlotte, NC), Share;; Paul
E. (Berwyn, PA), Fischer; Stephen A. (Yardley, PA) |
Assignee: |
Henkel Corporation (Plymouth
Meeting, PA)
|
Family
ID: |
22345803 |
Appl.
No.: |
08/112,779 |
Filed: |
August 26, 1993 |
Current U.S.
Class: |
162/6; 162/78;
162/79 |
Current CPC
Class: |
D21C
9/16 (20130101); D21C 5/02 (20130101); Y02W
30/64 (20150501); Y02W 30/648 (20150501) |
Current International
Class: |
D21C
9/16 (20060101); D21C 5/02 (20060101); D21C
005/02 () |
Field of
Search: |
;162/6,4,5,8,78,79 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Rydholm Pulping Processes, 1965 pp. 886 893 894..
|
Primary Examiner: Jones; W. Gary
Assistant Examiner: De Simone; Mark
Attorney, Agent or Firm: Szoke; Ernest G. Jaschke; Wayne C.
Grandmaison; Real J.
Claims
What we claim is:
1. A process for repulping wet-strength paper containing at least
one wet-strength resin comprising adding to a slurry of the
wet-strength paper at least one peroxide compound and a
catalytically effective amount of a non-alkali, non-alkaline earth
metal salt which is soluble in the slurry to thereby oxidize the
wet-strength resin during the repulping of the paper to form paper
fibers.
2. The process of claim 1 wherein the peroxide compound has the
formula (HOO).sub.n R wherein R is selected from the group
consisting of hydrogen, a straight or branched chain alkyl group
having 1 to 10 carbon atoms, an aryl group which may be substituted
with an alkyl group, or a terminal carboxyl radical, and n is 1 or
2.
3. The process of claim 2 wherein the peroxide compound is selected
from the group consisting of hydrogen peroxide, peracetic acid,
tert. butyl hydroperoxide, tert. amyl hydroperoxide, cumene
hydroperoxide and 2-5 dihydroperoxy-2,5dimethylhexane.
4. The process of claim 3 wherein the peroxide compound is hydrogen
peroxide.
5. The process of claim 3 wherein the peroxide compound is
peracetic acid.
6. The process of claim 1 wherein the amount of the peroxide
compound is at least 0.1% w/w of the dry fiber in the slurry.
7. The process of claim 6 wherein the amount of the peroxide
compound is at least 2.5% w/w of the dry fiber in the slurry.
8. The process of claim 7 wherein the amount of the peroxide
compound is from about 2.5 to 5.0% w/w of the dry fiber in the
slurry and the paper is a bleached paper.
9. The process of claim 1 wherein the wet-strength resin is at
least one resin selected from the group consisting of acid-curing
permanent resins, neutral/alkaline-curing permanent resins and
neutral/acid-curing temporary resins.
10. The process of claim 9 wherein the wet-strength resin is
selected from the group consisting of a
polyaminoamideepichlorohydrin resin and a polyamine-epichlorohydrin
resin.
11. The process of claim 1 wherein the amount of the metal salt is
sufficient to provide up to about 10 ppm of metal ion in the
slurry.
12. The process of claim 1 comprising adding a catalytically
effective amount of a non-alkali, non-alkaline earth metal salt
which is water-insoluble in said slurry and adding a reducing agent
to the slurry to convert the water-insoluble metal salt into a
compound which is soluble in said slurry.
13. The process of claim 1 wherein the metal of said metal salt is
a transition metal.
14. The process of claim 13 wherein the transition metal is
selected from the group consisting of iron, copper, cobalt, nickel,
manganese, silver, titanium, cerium, lead, chromium, vanadium,
molybdenum, tungsten, chromium, osmium and selenium.
15. The process of claim 14 wherein the metal is iron.
16. The process of claim 1 wherein said metal salt is ferrous
sulfate or ferrous ammonium sulfate.
17. The process of claim 1 comprising adding a metal chelate to
said slurry.
18. The process of claim 17 comprising forming the metal chelate by
reacting said metal salt with a chelating agent.
19. The process of claim 18 wherein said chelating agent is
selected from the group consisting of pentasodium
diethylenetriaminepentaacetic acid, ethylene diaminetetraacetic
acid, tetrasodium ethylenediaminetetraacetic acid, tetraammonium
ethylenediaminetetraacetic acid, disodium
ethylenediaminetetraacetic acid, diammonium
ethylenediaminetetraacetic acid, tetrasodium
diethylenetriaminepentaacetic acid, trisodium
N-(hydroxyethyl)-ethylenediaminetriacetic acid, and
triethanolamine.
20. The process of claim 19 further comprising combining the metal
salt or metal chelate with an anti-foaming wetting agent and then
adding the combination to the slurry.
21. The process of claim 1 wherein the slurry has a concentration
of paper in the range of from about 1 to 15% by weight.
22. The process of claim 1 comprising conducting the process at a
temperature of from about 25.degree. to 100.degree. C. at a pH of
from about 3 to 13.
Description
BACKGROUND
1.0. Field of the Invention
The present invention is generally directed to a process for
repulping wet-strength paper in which a peroxide compound alone or
in combination with a select group of metal salts or chelates
oxidizes polymeric resins in the wet-strength paper.
2.0. Discussion of Related Art
Wet-strength paper contains a resin which is adsorbed onto paper
fibers during the paper making process and cross-links on heating
or aging of the paper to form a polymeric network which adds
strength to the paper. Wet-strength resins fall into two groups,
permanent and temporary and include formaldehyde-based resins,
amine-epichlorohydrin based resins and aldehyde polymers.
In order to repulp wet-strength paper, it is necessary to hydrolyze
the cured resin. For many years metal hypochlorites (e.g. sodium
and potassium hypochlorite) have been used as reagents for
repulping wet-strength paper as shown by, for example, C. S.
Maxwell, U.S. Pat. No. 3,407,113 and H. R. Miller, U.S. Pat. No.
3,427,217.
Hypochlorites generate adsorbable organic halides in paper mill
effluents. These substances are environmentally undesirable.
Accordingly, the papermaking industry has sought to use
non-chlorinated reagents for repulping wet-strength paper.
Alkali metal persulfates (M.sub.2 S.sub.2 O.sub.8) and
monopersulfates (MHSO.sub.5) have recently been used as reagents to
replace hypochlorites. H. H. Espy et al "Persulfates as Repulping
Reagents for Neutral/Alkaline Wet-strength Broke" Tappi Journal
Vol. 76, No. 2, pp. 139-141 (February, 1993) show significant
reductions in organic chlorides using persulfates as the oxidizing
agent.
However, there is a continuing need to develop repulping reagents
that are environmentally acceptable and which are effective in
repulping wet-strength paper during the repulping operation.
3.0. Summary of the Invention
The present invention is generally directed to a process for
repulping wet-strength paper in which a non-chlorinated reagent is
used to oxidize the wet-strength resin in the wet-strength
paper.
In particular, the present invention is directed to a process for
repulping wet-strength paper comprising adding at least one
peroxide compound alone or in combination with a non-alkali,
non-alkaline earth metal salt or metal chelate to thereby oxidize
the wet-strength resin in the wet-strength paper to form paper
fibers.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides for the repulping of wet-strength
paper using, as an oxidizing reagent, at least one peroxide
compound alone or in combination with a non-alkali, non-alkaline
earth metal salt or metal chelate. In accordance with the
invention, the oxidizing reagent effectively oxidizes the
wet-strength resin in the wet-strength paper without producing
environmentally objectionable by-products such as occurs when using
hypochlorites.
The peroxide compounds employed in the present invention are
selected from those having the formula (HOO).sub.n R wherein R is
selected from hydrogen, a straight or branched chain alkyl group
having 1 to 10 carbon atoms, an aryl group which may be substituted
with an alkyl group, or a terminal carboxyl radical, and where n is
1 or 2. The preferred peroxide compounds are selected from the
group consisting of hydrogen peroxide, peracetic acid, tert. butyl
hydroperoxide, tert. amyl hydroperoxide, cumene hydroperoxide, and
2,5-dihydroperoxy-2,5-dimethylhexane. The most preferred peroxide
compounds are hydrogen peroxide and peracetic acid.
The amount of the peroxide compound employed in the present
invention is at least 0.1% w/w based on the dry weight of the dry
fiber in the slurry. It is preferred to have a concentration of the
peroxide compound of at least 2.5% w/w of the dry fiber in the
slurry, most preferably in the range of from about 2.5 to 5.0% w/w
of the dry fiber in the slurry for bleached wet-strength paper. A
somewhat greater amount of the hydroperoxide compound may be
required if the wet-strength paper contains lignin (e.g. brown
stock).
The metal salts which may optionally be used in combination with
the peroxide compound are selected from metal salts wherein the
metal is not an alkali metal (e.g. sodium and potassium) or an
alkaline earth metal (e.g. calcium and magnesium). The preferred
metals are selected from transition metals such as the group
consisting of iron, copper, cobalt, nickel, manganese, silver,
titanium, cerium, lead, chromium, vanadium, molybdenum, tungsten,
chromium, osmium and selenium. The most preferred metal is
iron.
The metal salts must be soluble in the aqueous slurry of the
wet-strength paper. Accordingly, the metal salts employed in the
present invention should be water-soluble or rendered water-soluble
in the slurry. The metal salt may be rendered water-soluble in the
slurry by adding a reducing agent. For example, ferric sulfate is
substantially water-insoluble. However, if ferric sulfate is
allowed to react with a reducing agent, such as, sodium
formaldehyde sulfoxylate or sodium metabisulfite, ferric sulfate
will be reduced to ferrous sulfate which is soluble in the aqueous
slurry. Other suitable reducing agents for use in the present
invention would be apparent to those skilled in the art. The
preferred metal salts for use in the present invention include
ferrous salts, such as, ferrous sulfate and ferrous ammonium
sulfate.
A chelating agent may be used to convert the metal salt to a metal
chelate. While any chelating agent may be used, the preferred
chelating agents include, pentasodium diethylenetriaminepentaacetic
acid, ethylenediaminetetraacetic acid (EDTA), tetrasodium EDTA,
tetraammonium EDTA, disodium EDTA, diammonium EDTA, tetrasodium
diethylenetriaminepentaacetic acid, and trisodium
N-(hydroxyethyl)-ethylenediaminetriacetic acid, and
triethanolamine. The preferred metal chelate is iron
diethylenetriaminepentacetic acid.
The metal chelate may be added to the peroxide compound to form a
reagent for oxidizing the wet-strength resin or may be formed in
situ by the reaction of a metal salt (e.g. ferrous sulfate) and a
chelating agent.
The amount of the metal salt or metal chelate which may be used in
the process of the present invention is an amount sufficient to
catalyze formation of alkoxy radicals in accordance with the
following equation:
wherein n=1 and x.gtoreq.1. The alkoxy radicals break the resin
bonds associated with the wet-strength paper. Generally, the amount
of the metal salt is sufficient to provide the slurry of the
wet-strength paper with up to about 10 ppm of the metal ion.
The repulping process is conducted by adding the peroxide compound
alone or in combination with the metal salt or metal chelate to the
aqueous slurry of the wet-strength paper. The repulping process is
conducted at a temperature typically in the range of from about
25.degree. to 100.degree. C., preferably from about 50.degree. to
80.degree. C.
The pH of the slurry will vary depending on the type of
wet-strength paper in the slurry. Generally, the pH of the slurry
will be in the range of from about 3 to 13. A pH of about 7 to 11
is generally used for repulping bleached wet-strength paper while a
pH spanning the entire range of from about 3 to 13 can be used to
repulp unbleached wet-strength paper.
The process is preferably carried out for slurries having a
concentration of wet-strength paper in the range of from about 1 to
15% by weight, preferably about 3 to 6% by weight, most preferably
about 5% by weight, regardless of the type of wet-strength paper
which is to be repulped.
The present process may be applied to oxidize all classes of
wet-strength resins from wet-strength paper. Generally,
wet-strength resins fall into three classes: acid-curing permanent
resins, neutral/alkaline-curing permanent resins and neutral/acid
temporary resins. Urea and melamine-formaldehyde resins are
exemplary of acid-curing permanent resins.
Polyaminoamide-epichlorohydrin and polyamine-epichlorohydrin resins
are examples of neutral/alkaline-curing permanent resins.
Polyacrylamide-glyoxal resins are examples of neutral/acid-curing
temporary resins. While the present process may be applied to
remove all classes of these resins from wet-strength paper,
particularly effective results are obtained when the wet-strength
paper contains the neutral/alkaline-curing permanent resins of the
polyaminoamide-epichlorohydrin or polyamine-epichlorohydrin
type.
The three classes of wet-strength resins and their particular
properties are known to those skilled in the art such as disclosed
in Herbert H. Espy "The Chemistry of Wet-Strength Broke Repulping"
Progress in Paper Recycling pp. 17-23 (August 1992).
The following examples are illustrative of embodiments of the
invention and are not intended to limit the invention as
encompassed by the claims forming part of the Application.
EXAMPLES 1-2
Example 1
Bleached milk carton paper board (40 grams) containing 0.4%
polyaminoamide-epichlorohydrin (PAE) wet-strength resin was cut
into 1".times.1" pieces and a pulp slurry of about 2% consistency
was prepared as described in Tappi Method T-205 om-88 section 7.1.1
by disintegrating for 2.5 minutes. The slurry was transferred to a
2 liter glass beaker, gentle stirring was applied, and the pH was
adjusted to 11 with 1N NaOH, and heated to 70.degree. C. Ferrous
sulfate (0.02 gram) and 3.3 grams of a 30% hydrogen peroxide
solution were added to the pulp slurry at 70.degree. C. The
temperature and pH were maintained for 32 minutes. A sample was
removed for filtering in a Somerville Fractionator having a 0.15 mm
slotted screen. Residuals were collected, dried overnight in an
oven at 105.degree. C. and reported as % repulped paper. Repulping
data was summarized in Table 1.
Example 2
Example 1 was repeated except that 3.1 grams of a 32% solution of
peracetic acid was added to the pulp slurry. The results are shown
in Table 1.
COMPARATIVE EXAMPLES A-E
Comparative Example A
Using the general repulping method of Example 1, 40.0 grams of milk
carton paper board were disintegrated for 2.5 minutes in 1,960
grams of water. The pulp slurry was transferred to a 2 liter beaker
and the pH was adjusted to 11 with 1N NaOH before heating to
70.degree. C. under gentle agitation. 1.0 gram of sodium persulfate
was added and the temperature and pH were maintained at 70.degree.
C. and 11, respectively. After 90 minutes, 75% of the paper was
repulped.
Comparative Example B
Comparative Example A was repeated, except that 1.0 gram of a
triple salt having potassium mono-persulfate as the active material
(Oxone; marketed by DuPont) was added to the pulp slurry. After 60
minutes, 93% of the paper was repulped.
Comparative Example C
Comparative Example A was repeated, except that 8.3 grams of a 12%
solution of sodium hypochlorite was added to the pulp slurry and
the pH was adjusted to 6.5 with 1N HCl. After 70 minutes, 98% of
the paper was repulped.
Comparative Example D
Comparative Example A was repeated, except that 0.02 gram of
ferrous sulfate was added prior to sodium persulfate. After 75
minutes, 92% of the paper was repulped
Comparative Example E
Comparative Example B was repeated, except that 0.02 gram of
ferrous sulfate was added prior to Oxone. After 30 minutes, 85% of
the paper was repulped.
A summary of Comparative Examples A-E is shown in Table 1.
TABLE 1 ______________________________________ % Time % Example
Additive Additive pH (Min.) Repulped
______________________________________ Example 1 H.sub.2 O.sub.2
/Fe 2.5 11 32 99.9 Example 2 CH.sub.3 CO.sub.3 H/ 2.5 11 32 97 Fe
Comparative A NPS 2.5 11 90 75 Comparative B MPS 2.5 11 60 93
Comparative C NaOCl 2.5 6.5 70 98 Comparative D NPS/Fe 2.5 11 75 92
Comparative E MPS/Fe 2.5 11 30 85
______________________________________ NPS = sodium persulfate MPS
= Oxone (DuPont) containing potassium monopersulfate NaOCl = sodium
hypochlorite Fe = 2 ppm iron in solution from ferrous sulfate
H.sub.2 O.sub.2 = hydrogen peroxide CH.sub.3 CO.sub.3 H = peracetic
acid
EXAMPLES 3-9
Example 3
Using the general repulping method described in Example 1, 40.0
grams of milk carton paper board containing 0.4% PAE were
disintegrated for 2.5 minutes in 1,960 grams of water. The pulp
slurry was transferred to a 2-liter beaker and the pH was adjusted
to 11 with 1N NaOH before heating to 70.degree. C. under gentle
agitation. 0.02 gram of ferrous sulfate followed by 3.3 grams of a
30% solution of hydrogen peroxide was added and the temperature and
pH were maintained at 70.degree. C. and 11, respectively. After 60
minutes, 91% of the paper was repulped as shown in Table 2.
Example 4
Example 3 was repeated, except that 0.02 gram ferrous sulfate
followed by 6.6 grams of a 30% solution of hydrogen peroxide was
added to the pulp slurry. After 60 minutes, 93% of the paper was
repulped.
Example 5
Example 3 was repeated, except 0.05 that gram ferrous sulfate
followed by 3.3 grams of a 30% solution of hydrogen peroxide was
added to the pulp slurry. After 60 minutes, 92% of the paper was
repulped.
Example 6
Example 3 was repeated, except the temperature was adjusted to
50.degree. C. and 0.02 gram ferrous sulfate followed by 3.3 grams
of a 30% solution of hydrogen peroxide was added to the pulp
slurry. After 60 minutes, 92% of the paper was repulped.
Example 7
Example 3 was repeated, except that 3.3 grams of a 30% solution of
hydrogen peroxide was added to the pulp slurry. After 60 minutes,
92% of the paper was repulped.
Example 8
Example 3 was repeated, except the temperature was adjusted to
35.degree. C. and 0.02 gram ferrous sulfate followed by 3.3 grams
of a 30% solution of hydrogen peroxide was added to the pulp
slurry. After 60 minutes, 85% of the paper was repulped.
Example 9
Example 3 was repeated, except the pH of the pulp slurry was
adjusted to 7 with 1N HCl, and 0.02 gram ferrous sulfate followed
by 3.3 grams of a 30% solution of hydrogen peroxide was added to
the pulp slurry. After 60 minutes, 99% of the paper was
repulped.
A summary of Examples 3-9 is shown in Table 2.
COMPARATIVE EXAMPLES F-H
Comparative Example F
Using the general method of Example 3, 40.0 grams of milk carton
paper board was disintegrated for 2.5 minutes in 1,960 grams of
water. The pulp slurry was transferred to a 2 liter beaker and the
pH was adjusted to 11 with 1N NaOH before heating to 70.degree. C.
under gentle agitation. 1.0 gram of sodium persulfate was added and
the temperature and pH were maintained at 70.degree. C. and 11,
respectively. After 60 minutes, 71% of the paper was repulped.
Comparative Example G
Comparative Example F was repeated, except that 1.0 gram of a
triple salt having potassium mono-persulfate as the active material
(Oxone; marketed by DuPont) was added to the pulp slurry. After 60
minutes 78% of the paper was repulped.
Comparative Example H
Comparative Example F was repeated without a repulping additive and
after 60 minutes, 76% of the paper was repulped.
A summary of comparative Examples F-H is shown in Table 2.
TABLE 2 ______________________________________ Time % Example
Additive % Additive pH (Min.) Repulped
______________________________________ Example 3 H.sub.2 O.sub.2
/Fe 2.5 11 60 91 Example 4 H.sub.2 O.sub.2 /Fe 5.0 11 60 93 Example
5 H.sub.2 O.sub.2 /Fe* 2.5 11 60 92 Example 6** H.sub.2 O.sub.2 /Fe
2.5 11 60 92 Example 7 H.sub.2 O.sub.2 2.5 11 60 92 Example 8***
H.sub.2 O.sub.2 /Fe 2.5 11 60 85 Example 9 H.sub.2 O.sub.2 /Fe 2.5
7 60 99 Comparative F NPS 2.5 11 60 71 Comparative G MPS 2.5 11 60
78 Comparative H None -- 11 60 76
______________________________________ NPS = sodium persulfate MPS
= Oxone (DuPont) containing potassium monopersulfate Fe = 2 ppm
iron in solution from ferrous sulfate H.sub.2 O.sub.2 = hydrogen
peroxide *5 ppm iron in solution from ferrous sulfate **reaction
temperature is 50.degree. C. ***reaction temperature is 35.degree.
C.
EXAMPLES 10-12
Example 10
Using the general repulping method of Example 1, 80.0 grams of
bleached poster board containing 1.0% PAE was disintegrated for
10.0 minutes in 1,920 grams of water. The pulp slurry was
transferred to a 2 liter beaker and the pH was adjusted to about 9
with 1N NaOH before heating to 70.degree. C. under gentle
agitation. 0.02 gram ferrous sulfate followed by 6.7 grams of a 30%
solution of hydrogen peroxide was added to the pulp slurry and the
temperature and pH were maintained at 70.degree. C. and 9,
respectively. After 75 minutes, 92% of the paper was repulped.
Example 11
Example 10 was repeated, except the pH was adjusted to about 11
with 1N NaOH and 0.02 gram ferrous sulfate followed by 6.7 grams of
a 30% solution of hydrogen peroxide was added to the pulp slurry.
After 55 minutes, 99% of the paper was repulped.
Example 12
Example 10 was repeated, except the pH was adjusted to about 11
with 1N NaOH and 3.4 grams of a 30% solution of hydrogen peroxide
was added to the pulp slurry. After 75 minutes, 73% of the paper
was repulped.
A summary of Examples 10-12 is shown in Table 3.
COMPARATIVE EXAMPLES I-K
Comparative Example I
The procedure of Example 10 was repeated except that 2.0 grams of a
triple salt having potassium monopersulfate as the active material
(Oxone; marketed by DuPont) was added to the pulp slurry in place
of ferrous sulfate and hydrogen peroxide. After 120 minutes, 57% of
the paper was repulped.
Comparative Example J
Comparative Example I was repeated, except that 2.0 grams of sodium
persulfate were added after the reaction temperature reached
70.degree. C. and another 2.0 grams was added after minutes
followed by 1.6 grams after 60 minutes for a total charge of 5.7
grams. After 210 minutes, 99.8% of the paper was repulped.
Comparative Example K
Comparative Example I was repeated without a repulping additive and
after 120 minutes, 51% of the paper was repulped.
A summary of Comparative Examples I-K is shown in Table 3.
TABLE 3 ______________________________________ Time % Example
Additive % Additive pH (Min.) Repulped
______________________________________ Example 10 H.sub.2 O.sub.2
/Fe 2.5 9 75 92 Example 11 H.sub.2 O.sub.2 /Fe 2.5 11 55 99 Example
12 H.sub.2 O.sub.2 /Fe 2.5 11 75 73 Comparative I MPS 1.3 12 180 72
Comparative J NPS 7.1 12 210 99.8 Comparative K None -- 12 120 51
______________________________________ NPS = sodium persulfate MPS
= Oxone (DuPont) containing potassium monopersulfate Fe = 2 ppm
iron in solution from ferrous sulfate H.sub.2 O.sub.2 = hydrogen
peroxide
EXAMPLES 13-18
Example 13
Using the general repulping method of Example 1, 40.0 grams of
unbleached liner board containing PAE was disintegrated for 5.0
minutes in 1,960 grams of water. The pulp slurry was transferred to
a 2 liter beaker and the pH was adjusted to about 4 with 1N HCl
before heating to 70.degree. C. under gentle agitation. 0.02 gram
of ferrous sulfate and 6.7 grams of a 30% solution of hydrogen
peroxide was added to the pulp slurry and the temperature was
maintained at 70.degree. C. After 120 minutes, 72% of the paper was
repulped.
Example 14
Example 13 was repeated, except the pH was adjusted to 4 with 1N
HCl and 0.02 gram of ferrous sulfate and 6.7 grams of a 30%
solution of hydrogen peroxide were added at 70.degree. C. After 60
minutes, the pH was adjusted to about 11 with 1N NaOH and 6.7 grams
of 30% hydrogen peroxide were added to the pulp slurry. After 120
minutes, 82% of the paper was repulped.
Preparation of Iron Chelate Complex
An iron chelate complex was prepared in the following manner. 1.0
gram of iron sulfate, hydrated with 7 moles of water, was dissolved
in 97.5 grams of water. 4.5 grams of an aqueous solution of
pentasodium salt of diethylenetriaminepentaacetic acid was added to
the iron sulfate solution and the pH was adjusted to 3.6 with 0.7
gram of hydrochloric acid (37% solution). The resulting solution
contained 1920 parts per million of chelated iron.
Example 15
Example 14 was repeated, except the pH was adjusted to about 4 with
1N HCl and 4.0 grams of chelated ferrous sulfate prepared as
described above was added. The slurry was heated to 70.degree. C.
and a total of 12.0 grams of 30% hydrogen peroxide was added in 15
minute intervals over a 60 minute period. The pH was adjusted to
about 11 with 1N NaOH and after 60 minutes, 81% of the paper was
pulped.
Example 16
Examples 16-18 were conducted to treat unbleached liner board
containing polyamine-epichlorohydrin resin.
Example 16 was otherwise a repeat of Example 13. After 120 minutes,
82% of the paper was repulped.
Example 17
Example 17 was otherwise a repeat of Example 14. After minutes, 89%
of the paper was repulped.
Example 18
Example 18 was otherwise a repeat of Example 14 except the pH was
adjusted to about 4 with 1N HCl and 0.02 grams ferrous sulfate was
added. The slurry was heated to 70.degree. C. and a total of 12.0
grams of a 30% hydrogen peroxide solution was added in 15 minute
intervals over a 60 minute period. The pH was adjusted to about 11
with 1N NaOH and after 60 minutes, 93% of the paper was
repulped.
A summary of Examples 13-18 is shown in Table 4.
COMPARATIVE EXAMPLES L-O
Comparative Example L
The procedure of Example 13 was repeated as Comparative Example L
except that 2.0 grams of a triple salt having potassium
monopersulfate as the active material (Oxone; marketed by DuPont)
were added to the pulp slurry in place of ferrous sulfate and
hydrogen peroxide. The temperature and pH were maintained at about
70.degree. C. and 11, respectively. After 120 minutes, 57% of the
paper was repulped.
Comparative Example M
Comparative Example L was repeated except that 2.0 grams of sodium
persulfate were added after the reaction temperature reached
70.degree. C. After 120 minutes, 57% of the paper was repulped.
Comparative Example N
Comparative Example L was repeated, except that 17.0 grams of a 12%
solution of sodium hypochlorite were added after the reaction
temperature reached about 70.degree. C. After 120 minutes, 61% of
the paper was repulped.
Comparative Example O
Comparative Example L was repeated, except that 6.0 grams of a 50%
NaOH solution was added after the reaction temperature reached
70.degree. C. After 120 minutes, 68% of the paper was repulped.
A summary of Comparative Examples L-O is shown in Table 4.
TABLE 4 ______________________________________ % Time % Example
Additive Additive pH (Min.) Repulped
______________________________________ Example 13** H.sub.2 O.sub.2
/Fe 5.0 4 120 72 Example 14** H.sub.2 O.sub.2 /Fe 10.0 * 120 82
Example 15** H.sub.2 O.sub.2 /Fe- 10.0 * 120 81 chelate Example
16*** H.sub.2 O.sub.2 /Fe 10.0 4 120 82 Example 17*** H.sub.2
O.sub.2 /Fe 10.0 * 120 89 Example 18*** H.sub.2 O.sub.2 /Fe 10.0 *
120 93 Comparative L** MPS 5.0 11 120 57 Comparative M** NPS 5.0 11
120 57 Comparative N** NaOCl 5.0 11 120 61 Comparative O** NaOH 7.5
11 120 68 ______________________________________ NPS = sodium
persulfate MPS = Oxone (DuPont) containing potassium monopersulfate
NaOCl = sodium hypochlorite Fe = 2 ppm iron in solution from
ferrous sulfate H.sub.2 O.sub.2 = hydrogen peroxide *pH at 4 for 60
min. and then adjusted to 11 **paper containing PAE resin ***paper
containing polyamineepichlorohydrin
Example 19
Using the general repulping method of Example 1, 20.0 grams of a
commercial polycoated orange juice container containing PAE resin
were disintegrated for 5.0 minutes in 1,000 grams of water. The
pulp slurry was transferred to a 2 liter beaker and heated to
60.degree. C. under gentle agitation. 0.02 gram of ferrous sulfate
and 1.7 grams of a 30% solution of hydrogen peroxide were added to
the pulp slurry and the temperature was maintained at 60.degree. C.
After 75 minutes, the batch was filtered and the polycoat and paper
residuals were separated and dried in an oven at 105.degree. C. for
2 hours. 3.4 grams of polycoat and 2.9 grams of fiber were
recovered. This was equivalent to 82.5% of the paper being
repulped.
Examples 1-19 show that by employing an oxidizing agent in
accordance with the present invention, the efficiency of repulping
was generally excellent without the production of undesirable
hypochlorites.
EXAMPLES 20-22
Example 20
40 grams of unbleached paper containing 1.0% PAE resin was cut into
1".times.1" pieces and slurried in 1960 grams of water. The slurry
was disintegrated for 15 minutes per the Tappi Method T-205 om-88
section 7.1.1. The amount of paper mechanically repulped was 47%.
The pH of the slurry was adjusted to 4 with 1N HCl, heated to
70.degree. C., and 0.02 grams of ferrous sulfate was added.
Hydrogen peroxide (12 grams of a 30% solution) was added in 15
minute intervals over a 60 minute period. The pH was adjusted to 11
with 1N NaOH and after 60 minutes, 58% of the paper was
repulped.
Example 21
40 grams of the same paper treated in Example 20 was cut into
1".times.1" pieces and slurried in 1960 grams of water. The pH was
adjusted to 4 with IN HCl while heating the slurry to 70.degree. C.
0.02 gram of ferrous sulfate was added followed by 13.2 grams of
30% hydrogen peroxide over a 60 minute period. The pH was adjusted
to 11 with 1N NaOH and the slurry was mixed for another 60 minutes.
The slurry was disintegrated for 3 minutes in the same manner as
Example 20. The amount of paper repulped was 91%.
Example 22
40 grams of the same paper treated in Example 20 was cut into
1".times.1" pieces and slurried in 1960 grams of water. The pH of
the slurry was 8.2 and the slurry was heated to 70.degree. C. 0.02
gram of ferrous sulfate was added followed by 13.2 grams of 30%
hydrogen peroxide and the slurry was mixed for 30 minutes. The pH
was adjusted to 11 with 1N HCl and mixed for another 30 minutes.
The slurry was disintegrated for 3 minutes in the same manner as
Example 20. The amount of paper repulped was 80%.
Examples 20-22 show that a greater amount of paper may be repulped
when the resin containing paper was first treated with the
oxidizing reagent of the present invention followed by mechanical
disintegration of the paper.
* * * * *